Magnetic torque apparatus



A. WINTHER MAGNETIC TORQUE APPARATUS Jan. 22, 1952 3 Sheets-Sheet 1Filed Aug. 26, 1946 Jan. 22, 1952 A. WINTHER MAGNETIC TORQUE APPARATUS 3Sheets-Sheet 2 Filed Aug. 26, 1946 FIG.4.

uDOGOk P-ANGULAR VELOCITY- STATIC lNlT ANGULAR DISPLA IAL CEMENT A.WINTHER MAGNETIC TORQUE APPARATUS Jan. 22, 1952 3 Sheets-Sheet 5 FiledAug. 26, 1946 FIG.||.

Patented Jan. 22, 1 952 MAGNETIC TORQUE APPARATUS Anthony Winther,Kenosha, Wis., assignor to Martin P. Winther, as trustee, Waukegan, Ill.

Application August 26, 1946, Serial No. 693,056

Claims.

This invention relates to magnetic torque apparatus, and with regard tocertain more specific features, to a magnetic coupling for clutches,brakes, dynamometers and the like.

Among the several objects of the invention may be noted the provision ofa magnetic coupling between elements, in which a high and, if desired,constant torque may be obtained over a wide range of slip speeds of saidelements, including zero slip speed; the provision of a coupling of theclass described in which there is no energy lost in the couplin if theload does not exceed the static holding power of the device, said staticholding power being high; the provision of a coupling of this class inwhich predetermined torque values, including constant values, may beefiected under slip conditions involving torques above the staticholding torque; the provision of apparatus of this class which inoperation under both static and slip conditions stores some energy whichafter operation becomes useful upon its recovery, for example, to'

prevent backlash in various apparatus; and the provision of apparatus ofthis class which is particularly useful when applied to tension controlon reels, weaving, drawing, spooling machines and the like. Otherobjects will be in part apparent and in part pointed out hereinafter.

The'invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawings, in which several of various possibleembodiments of the invention are illustrated,

Fig. 1 is an end elevation of an elementary form of the invention;

Fig. 2 is a top plan view of Fig. 1;

Fig. 3 is an enlarged diagrammatic view of certain parts of Figs. 1 and2, illustrating certain functions believed to occur;

Fig. 4 is a curve showing certain torque-displacement relationships;

Fig. 5 is a sectional view of another form of the invention, being takenon line 55 of Fig. 6;

Fig. 6 is a longitudinal section taken on line 5-6 of Fig.

Fig. 7 is a longitudinal section of another form of the invention, beingtaken on line I'I of Fig. 8;

Fig. 8 is a vertical section taken on line 8-8 of F1:-

Fig. 9 is a longitudinal section (partly in elevation) of a reelembodying one form of the invention; and,

Figs. l0, l1 and 12 are vertical sections taken on lines Ill-I0, Il-lland l2|2, respectively, of Fig. 9.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Electromagnetic couplings have heretofore been used wherein the couplingaction was effected primarily by magnetic reactions from engendered eddycurrents. Such couplings were effective to transmit torque only underconditions of slip movement between the driving and driven elements. Thetorque-transmitting functions of the present invention are made todepend upon other factors than merely eddy-current losses, although theeffects of the latter may be taken advantage of, if desired. The resultis the ability of the present device (1) to transmit torque without slipup to a certain torque value, and thereafter (2) to transmit either aconstant or a rising torque with slip, as desired. In addition, thedevice under condition (1) exerts a restorative torque action withoutdissipation of energy.

Referring now more particularly to Figs. 1 and 2, numeral 1 indicates astrong, permanent horseshoe magnet providing a strong magnetic field. Apermanently polarized Alnico magnet is satisfactory. Attached areoppositely located taper pole pieces 3 and 5, composed, for example, ofsoft iron. Soft iron is exemplary of any material which has a highmagnetic permeability but preferably of low retentivity, that is, itaccepts a dense flux which may be easily coerced so that flux change ordistortion therein may easily be accomplished. The purpose of this isthat a pole shift may easily be made to occur, as will appear. However,the pole pieces retain their respective polarities. Between the polepieces 3 and 5 are non-magnetic bearing plates 1 providing bearings fora shaft 9 which carries a rotor II. This rotor II is composed ofmagnetic material having the characteristics of high remanence and highretentivity; that is, it is difficult to coerce so that flux change ordistortion therein is difficult. A suitable material for the rotor isAlnico V metal, chilled cast' iron or the like. The rotor is notpolarized before assembly and receives polarization only by magneticinduction from the pole pieces 3 and 5. Alnico is, in general, asintered alloy containing iron, aluminum, nickel and cobalt. It is to beunderstood that other similar alloys having 3 corresponding propertiesmay be suitable and that the terms Alnico and Alnico V are used simplyto designate suitable material that can be obtained in the electricaltrade. The rotor l l is cylindric, having relatively uninterrupted facesopposite the pole pieces 3 and 5, thus providing a relatively smoothsurface into which may enter concentrated flux from said pole pieces 3and 5. The rotor ll may be laminated or non-laminated as desired, anon-laminated construction being shown in Figs. 1 and 2. The eifectsoflaminations or their absence will be discussed below. It will beadditionally noted that.

the pole pieces 3 and 5 have faces which envelope the cylindric inductormember If overasubstantial portion of its periphery; for example, abouthalf the periphery.

At numeral 13 is shown a magnetic bar hinged to one of the poles 3 by amagnetic hinge l5 and having a magnetic adjustable screw support I! onthe other pole 5-.- Since all of-the members I3, 15 and I! are magnetic,this provides an adjustable by-pass for the magnetic circuitwhichotherwise would all--pass between poles 3 and 5 through the rotorII. The higher the bar I3 is adjusted the less by-passage of the fluxisaccommodated, and vice versa. This device serves as a torque controlmeans when the indicated permanent magnet field means is used.

Figs. 3 and 4 are diagrams which will aid in an understanding of theoperation of the invention. In diagrammatic Fig. 3 the magnetic bypassmeans has been eliminated. Assume that under the magnetizing influenceof the magnet l, the field pole 3 is south and the field pole 5 isnorth. The induced poles in the rotor l I will be of oppositepolarities. If the rotor I l is not rotating, these poles willall lie upon line AA and no torque will be exerted (see the dotted letters N andS). If the rotor I l is turned by means of shaft 9 in the clockwisedirection (Fig. 3), the induced poles N and'Sin the rotor will tend tomove to the angular position shown by the solid letters N and S in therotor. Since the material of the rotor has a relatively highretentivity,

these poles will not tend to vary so quickly as would be the case if therotor had a relatively low retentivity. Also, since the pole pieces havelow retentivity, their strong magnetic poles easily become distorted orshifted to the solidNand S positions indicated'in the pole pieces. Thusthe highly retentive poles in the rotor tend to move with the rotorinstead of being displaced therein.

Since the poles in the low retentive pole pieces tend respectively tofollow the highly retentive moving poles in the rotor, each pair ofpoles consisting of an inducing and induced pole, moves to a positionwherein their inutualqstatic attractions exert a very substantial torquearound the center line of the. shaft 9. This torque reacts against thetorque appliedto the shaft 9., At a very small angular displacementthese torques will balance statically. It is to be notedthat the northand south members of each pair of poles,

remain closer to one another than, they would Without flux shift in thepole pieces .3 and 5. Hence their attractive actions remain high. It isalso to be noted that each north and south rotor pole will, with arepulsive action, approach the next respective shifted north or southpole in the respective pole piece. This adds to the resistance set upagainstthe applied'torque; Consequently the static holding power of thedevice after a small angular displacement is very great. The highretentivity in the rotor requires strong fields in the pole pieces toeffect the desired polar conditions in the rotor, and that is one reasonfor employing the highly permeable soft iron pole pieces, which have ahigh induction constant. In such pole pieces, strong, but readilyshiftable poles can be maintained for their inductive and attractiveeffect upon the rotor.

The attraction between pairs of inducing and induced poles is so greatin apparatus when built as described, that a static resisting torque toapplied torque, without slip, has been attained exceeding 1 lb. inchtorque per square inch of rotor surface. This was in the case of amachine having a rotor only 9e inch long and only '1 inch in diameterwith a :9 inch air gap between the rotor and the pole pieces.

Any reduction of. the applied static torque resultsrin the rotorreturning to its initial position, all energy stored in the flux fieldtensions being returned as mechanical work. This energy storing1 featuremay be used to eliminate backlash in reeling mechanisms; as will appear.

The above-described static reacting torque is independent of angularvelocity and dependsupon angular displacement only, as indicated at theleft in Fig. 4. Time is not important. From a startingposition S thetorque increases suddenly within an initial angular displacement of theorder of 15 or so, which is independent of angular velocity. In Fig. 4this relationship is plotted on the leftside of the zero verticalordinate.

In the drawing, Static initial angular displacement along line SO refersto that displace.- ment which occurs with torque reaction but with outthe necessity for any appreciable angular velocity to bring about suchreaction. As soon as the applied torque which is indicated over 0 inFig. 4 is exceeded, slip sets in, which is to say that a condition ofrelative angular velocity comes into existence between the rotor II andthe pole pieces 3 and 5."

Assuming the rotor I I to be formed of Alnico," or laminated, both ofwhich inhibit eddy-current losses, the torque will remain substantiallyconstant at any angular velocity except for a very slight rise that isdue (1) to small amounts of eddy currents that flow even in laminated orlike structures and (2') to hysteresis losses. Deviations from constancyof torque under slip conditions depend primarily upon the eddy currents,provided they are allowed to flow in the rotor. As stated, Alnicoinherently inhibits eddy currents. If the rotor is composed of chilledcast iron or the like, eddy currents will be inhibited by laminating itand torque constancy approached. If eddy currents are not inhibited, thetorque curve will rise more steeplywith increased angular velocity. InFig. 4 the slightly rising characteristic for torque with risingvelocity or slip speed is shown to exist because, even with an Alnico ora laminated rotor, a few eddy currents will appear and some hysteresisloss occurs.

If Alnico metal is used for therotor, lamination need not be resorted.to for reducing eddy currents because this materialduring the sinteringprocess usedfor its manufacture evolves an inherently high internalresistance to the flow of eddy currents.

It is to be understood that even if torque builds up with speed, as wheneddy currents are permitted to flow, neverthless there is still retaineda sudden rise in torque (with angular displacementfrom an initialreference position) which is independent of angular velocity up to acertainpoint, as indicated over S-O in Fig. 4. The only difierencetherefore between a solid rotor and a laminated or the equivalent rotoris that in the solid-rotor case eddy currents are generated and reactingtorque increased to a certain extent with increased speed, but in thecase of a laminated rotor or the equivalent, this is not true. lynoticeable with thin laminations and increases with speed as thelamination thickness increases. However, an important point to be keptin mind is the structure which produces substantial reacting torqueindependently of speed, that is to say, the part of the action indicatedin Fig. 4 above line 8-0. Under conditions of substantial angularvelocity a substantially rising torque depends primarily upon theproduction of eddy currents.

It will be understood that if up to the zero ordinate in Fig. 4 themoment applied to the rotor be reduced, the rotor will move toward itsinitial position and upon removal of all torque it will substantiallyreach that position. This is because internal losses under non-slipconditions are almost nil.

In Figs. 5 and 6 is shown a construction wherein both the field and theinductor members are made rotary and wherein instead of a permanentmagnet an electrical coil is used for magnetization. In this case,pedestals |9 support a rotary shaft 2| which carries a cylindric rotor23, the latter in this case being shown laminated and composed, forexample, of chilled cast iron. Rotary on the shaft 2| are end bells of afield member. These end bells are preferably nonmagnetic and arefastened to a magnetic ring 21 having pole pieces 29. Wound upon thepole pieces are field coils 3| which are fed with direct current from asource of current 32 through slip rings 33. At 35 is shown a rheostatfor controlling the fiow of current through the coils 3| and hence theintensity of the fiux fields emanating from the pole pieces 29. It is tobe understood that the pole pieces 29 are again composed of materialsimilar to that of the pole pieces of Fig. 1 and that the coils arewound to produce opposite N and S polarities in these poles. If one orthe other of the relatively rotary members of Figs. 5 or 6 is caused tofunction as a rotary driving member, a reacting torque will beengendered. If the resisting torque on the driven member is equal to orless than the torque at which slip will occur, the driven member may bedriven by means of the driving member without slip. After this torque isexceeded, slip occurs. This construction may be used as a coupling forclutch or dynamometer constructions. It will be seen that if the drivenmember is operating an item such as a winding and tensioning spool, whenthe driving action stops, any strand being tensioned by the spool willremain in tension provided the driving member is not retracted from theposition in which it stops. Thus Figs. 5 and 6 show how the inventionmay be applied to apparatus in which a slip coupling is desired havingthe characteristics above specified.

In Figs. 7 and 8 is shown another form of the invention similar to thatshown in Figs. 5 and 6, except that the rotor is in the form of anonlaminated disc made, for example, of chilled cast iron, and the fieldmembers present unlike magnetic poles on opposite sides of the disc.According to these Figs. 7 and 8, numeral 31 indicates the support forgudgeons 39 of a rotary field supporting frame 4|. Within this frame 4|is a The reacting torque increase will be hardrotary shaft 43 on whichis the inductive rotor 45. The member 4| carries two C-shaped polepieces 46 on the legs of which are windings 41 producing north and southpoles at 49 and 5|, respectively. The pole pieces at 49 and 5|, are, forexample, made of soft iron. Current is fed to the coils 41 through sliprings 53 from a source of current 54 and via a controlling rheostat 55.The action is the same as in Figs. 5 and 6 except that in this case thetorque-producing attractive action between the poles of pole pieces 49or 5| on the one hand, and the resulting induced poles in the rotor 45is tangential to the sides of the disc.

In Figs. 9-12 is shown an application of the invention to a reel.Referring to these Figs. 9-12, numeral 51 indicates the non-magneticframe of the reel in which is the rotary reel 59 for the line. Thestrand to be reeled is not shown. The reel is mounted upon a rotaryshaft 6| on which is carried an Alnico or like cylindric rotor 63 madeaccording to the above principles. Fastened in the end of the frame is apair of soft iron pole pieces 65, which envelope the rotor over I asubstantial portion of the periphery; or as shown, more than half theperipheral surface of the rotor. Between the pole pieces is an Alnicopermanent bar magnet 61 which magnetizes the pole pieces 65 to oppositepolarities. On the frame 51 is a non-magnetic rotary cover 69 havingcircular guide slots ll. One of the slots cooperates with a headed pin13 and the other with a headed screw 15. By loosening the screw 15 andturning the cover 69 it may be adjusted to various angular positions.Within a recess in the cover is solidly positioned a magneticallypermeable bar 11 which, due to the adjustable characteristics of thecover 69, may be set anywhere between either of two right-angularpositions, such as indicated by the solid and dotted lines in Fig. 12.Thus the magnetic circuit of the bar magnet 61 which ordinarily passesthrough the pole pieces 65 and through the rotor 63 may beshort-circuited in part so as to modify the magnetic strengths of thepole pieces 65.

When a strand on the reel pays out, it will spin the reel 59. which inturn spins the rotor 63. A magnetic braking action occurs between therotor and the pole pieces 65. As illustrated in Fig. 4, the resistingtorque immediately builds up to a certain value. This occurs during thefirst few degrees of movement of the rotor 63. This resisting torque isnot substantially exceeded, even at high angular velocities of the reeland rotor. This means that the strand on the reel pays off with correctconstant braking action, as determined by adjustment of the bar 11. Thepredetermined braking action is still effective up to the last degree ofmovement, preventing the occurrence of slack or backlash in the strand.In other words, the reel 59 does not overrun and tend to snarl thestrand. This is due to the backlash take-up effect of the existingreactive torque at the final position (zero speed) of the rotor 63.

The above is only one example of many applications in which slack orbacklash may effectively be kept out of material being paid from or to areel or the like at the end of a reeling operation, and without havingexcessive braking action built up during said reeling operation.

From the above it will be seen that there is also provided means forconstructing an electromagnetic coupling in which there is no loss ofenergy if the load does not exceed the static holding power of thecouplingbecause under such.

static holding conditions there is-no slip,

In the application. of the inventionto a continuously, operatingelectric slip clutch, there might be some loss of energy in. thecoupling during the time that a loadis picked-up; that is,

slip, might occur under the larger-torque conditions:.required foraccelerating the load,- but" after the acceleration is completed thelighter runningtorque may'cften'be carriedunder the.-

non-slip. conditions between driving and driven memberswithoutxlosspienergyin the coupling.-

In: the above-disclosure certain explanations.-

have been made of the functioning of my invention; Thishasbeen for thepurpose of explaining; .so far asI am able, the improved results.obtainedbymyncwapparatus. It is to be under stood; however, that theresults obtained do not depend; upon. such explanations'and they areofieredonly-in theinterest of producing a disclosure which is asolear asI am able to make it. It is .of course clear that otherand possiblybetter explanations do not affect the physical character of theimprovement.

In connection with possible alternative explanations, it-may., beobserved that in the case of rotor materials having high retentivityandhigh remanence there is usually associated a hysteresisloopofsubstantiai area. The existence ofsuch a-loop mayhelp ;to explainthe-operation. Thus, in the case of apparatus in which eddy currentshavebeen inhibited in the rotor by the use; of Alnico, or laminations,any rising characteristic of the torque curvein Fig. 4 beyond.

point O.may, in part be due to hysteresis losses. I have .-.observedthat the maximum torque available depends upon the shape of thehysteresis loop andthe area covered by it, and that maximum torque isobtained when the field strength is sufiicient to operate the rotor justinside the hysteresis. loop. This is no doubtdue to the fact thathysteresis losses in a givenmaterial cannot be. extended beyond thosethat are measured bythe area of the loop, and-since this area ispredetermined for. each material, it is a measure ofthe torque limit,ignoring eddy-current losses;

It should be noted in this connection that the meansfor adjusting theflux through the inductor, as shown in Figs. 1, 2, and. 9-12, providemeans for operating at maximum torque reaction when desired, under anyconditions of operation to which the apparatus may be subjected. Thisunder static conditions cannot be maintained.

under slip conditions because under the slip conditions the oppositepoles break away, from one another and there is a tendency to drop. thetorque load entirely. That is not true of the present invention.

butwill not operatesatisfactorily under static torque conditions, beingmore like, although not the same as, which employed the eddycurrents.,for transmitting torquesunder slip conditions only.

For the purpose of this specification, the term remanence is defined asthe magnetic induction Squirrel-cage and similar. constructions mayoperate under slip conditions.

former. homogeneous inductors which remains, in a: materialv after theremoval Retentivity of.- an applied magnetomotive force. is the-propertyof the; material which-is measured by. the: residual induction thereincorresponding to: its saturation induction.

mines, ,under givenconditions, the magnitude relation between magneticinduction and magnetizingforcein the material.

Definitions. ofv Electrical Terms," published. by

The American Instituteof Electrical Engineers,

approved- 1941..

The term torque couplingas usedherein refers to. either a clutch orbrake.

Although the pole pieces in the above de scription-of Figs; 1, 2,- 5,.6,- 9. and 11 are shown as being outside of the relativelyuninterrupted,

interior inductor, it will be v understood that this relationship may bereversed without changein principle.

In view of-the-above, itwill be seen that the several objects'of theinvention-are achieved and other advantageous results attained.

As many changes could be made in the above constructionswithoutdeparting from thescope ofthe invention, it is intendedthatall matter.containedin the above descriptionor shown in the accompanying drawingsshallbev interpreted ber having-spaced pole pieces of. relatively low.retentivity high-permeability magnetic .material.

inmagnetic inductiverelation to the inductor membenithe inductor memberhaving a sweep surface, which is-relatively uninterrupted withrespect-tothespaced. pole pieces and beingpolarized primarily by thepole pieces, saidinductor member beingconstructed of magnetic materialhaving characteristics of high hysteresis-loss; and means .for producingnon-alternating-poles insaid pole" pieces comprising a permanent magnet.

2.*A*substantially constant-torque slip coupling: as set forth in claim1 further including an adjustably positionable memberof magneticmaterial Whichismovable toward and away from thepole-picces foradjustably by-passing portions of the-flux-at-the pole pieces.

3. Awsubstantially constant-torque magnetic tensioning brake comprisingarotor and a stator, the stator having-apolarized permanent magnet ofhigh-retentivity magnetic materialand pole pieces of low-retentivitymagnetic material at thepolar-ends of the-magnet, the rotor having asmooth annular sweep surface adjacent the pole pieces and; being formedof eddy-current inhibiting and high-hysteresis-loss magnetic material;the'rotor beingpolarized solely by the.

pole' pi'eces;

4. Ina pa'y-Offreel; a-magnetic inductor member driven. by the reelanda'magnetic field member secured to'the frameoithe reel, the field.

member having a polarized permanent magnet of high retentivity magneticmaterial and pole pieces of low-retentivity magnetic material at the,polar ends of the magnet, the inductor member having asmooth annularsweep surface adjacent the pole pieces formed of eddy-currentinhibiting, and

Perms-- ability isthepropertyl-of a materialwhich deter- Thesedefinitions correspond'to those given in American Standardlow Speedcomprising relatively rotary magnetic field and magnetic inductormembers, the inductor member being in the shape of a cylinder and beingcomposed of high-hysteresis-loss magnetic material at least at theperiphery thereof, the field member having pole pieces of 10W-retentivity high-permeability magnetic material enveloping the inductorover a substantial portion of its periphery, and means for producing anon-alternating field in said pole pieces comprising a permanent magnet,the inductor being polarized only by the pole pieces.

ANTHONY WINTHER REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 396,602 Rice Jan. 22, 18891,308,435 Maire July 1, 1919 Number Name Date 1,424,769 Morrison Aug. 8,1922 1,531,389 Gordon Mar. 31, 1925 1,546,269 Warren July 14, 1925 51,665,613 Tanner Apr. 10, 1928 2,056,177 Erbguth Oct. 6, 1936 2,070,447Morrill Feb. 9, 1937 2,183,404 Morrill 1. Dec. 12, 1939 2,241,983Connolly May 13, 1941 1) 2,373,609 Stahl Apr. 10, 1945 2,386,505 PuchyOct. 9, 1945 2,390,877 Fisher Dec. 11, 1945 FOREIGN PATENTS NumberCountry Date 458,671 Great Britain Dec. 18, 1936 OTHER REFERENCESExperimental Electrical Engineering, Karapetoff, vol. 1, second edition,published in 1910 by John Wiley and Sons, New York city. pages 190 to195.

